Device for absorbing kinetic energy of a moving body

Abstract

Device for absorbing kinetic energy of a moving body includes a plastically deformable helical spring having a stack of convolutions, the inner surfaces of which delimit a passage. At least a part of the convolutions can be pulled successively through the passage. Due to the resulting deformation of the convolutions, energy can be absorbed.

The invention claimed is: 
     
       1. A device for absorbing kinetic energy of a moving body, comprising:
 a tension member which comprises a plastically deformable helical spring having a single stack of convolutions, 
 the stack of convolutions having a first part including at least one convolution, an inner surface of the first part of the stack of convolutions defining a passage, 
 the stack of convolutions having a second part including at least one convolution, each of the at least one convolution in the second part of the stack of convolutions having a diameter smaller than a diameter of the at least one convolution in the first part of the stack of convolutions and a pitch larger than a pitch of the at least one convolution in the first part of the stack of convolutions arising from deformation of the at least one convolution in the second part of the stack of convolutions relative to the at least one convolution in the first part of the stack of convolutions, 
 at least a portion of the second part of the stack of convolutions being situated in the passage defined by the first part of the stack of convolutions; and 
 stop means for retaining a position of the stack of convolutions, the stop means comprising a support that supports the first part of the stack of convolutions, the support including a through-hole communicating with the passage defined by the first part of stack of the convolutions, at least a portion of the second part of the stack of convolutions being situated in the through-hole in the support. 
 
     
     
       2. The device according to  claim 1 , wherein the stop means further comprise a stop surface that blocks displacement of the first part of the stack of convolutions laterally to a direction of extension. 
     
     
       3. The device according to  claim 2 , wherein the support and the stop surface are part of a casing, the casing including a step on which an extreme one of the convolutions in the first part of the stack of convolutions rests. 
     
     
       4. The device according to  claim 2 , the first part of the stack of convolutions projects over the stop surface as viewed in the direction of extension of the passage. 
     
     
       5. The device according to  claim 1 , wherein the support is a casing and the stop means further comprise a supporting plate having an aperture through which part of the casing defining the through-hole passes. 
     
     
       6. The device according to  claim 5 , wherein the casing includes a step on an inner surface, the first part of the stack of convolutions resting on the step. 
     
     
       7. The device according to  claim 5 , wherein the casing includes a side wall that surrounds only a portion of the first part of the stack of convolutions to thereby limit lateral extension of the at least one convolution in the first part of the stack of convolutions. 
     
     
       8. The device according to  claim 1 , wherein the stop means further comprise a ring arranged on the support, the ring surrounding only a portion of the first part of the stack of convolutions. 
     
     
       9. The device according to  claim 8 , wherein the ring rests on and is connected to the support. 
     
     
       10. The device according to  claim 1 , wherein the through-hole in the support has a diameter that corresponds to at least an internal diameter of the first part of the stack of convolutions. 
     
     
       11. The device according to  claim 1 , wherein before stressing the device by means of the body, an end of the helical spring adjacent the second part of the stack of convolutions projects into the passage of the first part of the stack of convolutions or is passed through the passage defined by the first part of the stack of convolutions. 
     
     
       12. The device according to  claim 1 , wherein the at least one convolution in the first part of the stack of convolutions comprises a plurality of convolutions, and the convolutions of the first part of the stack of convolutions have substantially the same diameter. 
     
     
       13. The device according to  claim 1 , wherein the at least one convolution in the first part of the stack of convolutions comprises a plurality of convolutions, and the convolutions of the first part of the stack of convolutions have a diameter that becomes constantly greater or smaller at the start and/or end of the stack of convolutions. 
     
     
       14. The device according to  claim 1 , wherein the tension member is made of wire, the tensile strength of which is at least 500 N/mm 2  and/or maximum 2000 N/mm 2 . 
     
     
       15. The device according to  claim 1 , wherein the tension member is made of steel wire which has a round cross-section and/or is corrosion-resistant. 
     
     
       16. The device according to  claim 1 , wherein the surface of the at least one convolution of the first part of the stack of convolutions is treated to be smoother and/or more wear-resistant. 
     
     
       17. The device according to  claim 1 , further comprising a protective hood arranged over and around the first part of the stack of convolutions. 
     
     
       18. The device according to  claim 1 , wherein the second part of the convolutions extends outward from the through-hole. 
     
     
       19. The device according to  claim 1 , wherein the helical spring consists of a single wire. 
     
     
       20. The device according to  claim 1 , wherein the first part of the stack of convolutions is positioned such that the passage defined thereby aligns with the through-hole in the support.